This invention relates to permanent magnetic alloys and, in particular, to rare earth-cobalt system permanent magnetic alloys.
Among the intermediate substances of RCo.sub.5 and R.sub.2 Co.sub.17 intermetallic compounds, those which are composed of R(CoFeCu)z (z=5-85) where the Co or Co and Fe components have been partially substituted with Cu are known to be excellent material for permanent magnets, see, for example, U.S. Pat. No. 3,560,200. In recent years, rather than the high coercive force (.sub.1 Hc) of rare earth-cobalt magnets, high residual magnetic flux density (Br) is in demand from applied fields. Thus, the main stream of rare earth magnets is shifting from the .sub.1 Hc-dominant 1-5 system sintered magnets to Br-dominant 2-17 system magnets.
It is disclosed in Japanese Patent Application 52-154207, which is incorporated herein by reference, that alloys of (Sm, Y) (Co, Fe, Cu)z composition in which the R component consists of Sm and Y result in a permanent magnet with a high Br value of approximately 11KG while maintaining the coercive force of above 3KOe. However, in the case of rare earth magnets, due to the low value (3-6KOe) of coercive force, their application is limited by the fact that the maximum efficiency is obtained when used on the side of relatively high permeance coefficient (B/H=2-5) with respect to the magnet circuit.